Search NASA⌕ Search

SEARCH · Search NASA

Results for “core shell”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

ADAS Update and Maintainability

Since 2000, both the National Weather Service Melbourne (NWS MLB) and the Spaceflight Meteorology Group (SMG) have used a local data integration system (LOIS) as part of their forecast and warning operations. The original LOIS was developed by the Applied Meteorology Unit (AMU) in 1998 (Manobianco and Case 1998) and has undergone subsequent improvements. Each has benefited from three-dimensional (3-D) analyses that are delivered to forecasters every 15 minutes across the peninsula of Florida. The intent is to generate products that enhance short-range weather forecasts issued in support of NWS MLB and SMG operational requirements within East Central Florida. The current LDIS uses the Advanced Regional Prediction System (ARPS) Data Analysis System (AD AS) package as its core, which integrates a wide variety of national, regional, and local observational data sets. It assimilates all available real-time data within its domain and is run at a finer spatial and temporal resolution than current national or regional-scale analysis packages. As such, it provides local forecasters with a more comprehensive understanding of evolving fine-scale weather features. Over the years, the LDIS has become problematic to maintain since it depends on AMU-developed shell scripts that were written for an earlier version of the ADAS software. The goals of this task were to update the NWS MLB/SMG LDIS with the latest version of ADAS, incorporate new sources of observational data, and upgrade and modify the AMU-developed shell scripts written to govern the system. In addition, the previously developed ADAS graphical user interface (GUI) was updated. Operationally, these upgrades will result in more accurate depictions of the current local environment to help with short-range weather forecasting applications, while also offering an improved initialization for local versions of the Weather Research and Forecasting (WRF) model used by both groups.

Watson, Leela R.↗
NASA NTRS1984

Thermal evolution of Venus

A modification of the Boussinesq fluid assumption is the basis of the present theory of three-dimensional and finite amplitude convection in a viscous spherical shell with temperature- and pressure-dependent physical parameters. The theory is applied to the definition of thermal evolution models for Venus which emphasize the effects of certain physical parameters on thermal evolution, rather than the specific thermal history of the planet. It is suggested that a significant portion of the present temperature in the mantle and surface heat flux of Venus is due to the decay of a high temperature that was established in the planet at the completion of its core formation, and that Venus has been highly convective over the course of its history, until about 0.5 Ga ago.

Arkani-Hamed, J.↗
NASA NTRS2015

NASA's Space Launch System Program Update

Hardware and software for the world's most powerful launch vehicle for exploration is being welded, assembled, and tested today in high bays, clean rooms and test stands across the United States. NASA's Space Launch System (SLS) continued to make significant progress in 2014 with more planned for 2015, including firing tests of both main propulsion elements and the program Critical Design Review (CDR). Developed with the goals of safety, affordability, and sustainability, SLS will still deliver unmatched capability for human and robotic exploration. The initial Block 1 configuration will deliver more than 70 metric tons of payload to low Earth orbit (LEO). The evolved Block 2 design will deliver some 130 metric tons to LEO. Both designs offer enormous opportunity and flexibility for larger payloads, simplifying payload design as well as ground and on-orbit operations, shortening interplanetary transit times, and decreasing overall mission risk. Over the past year, every vehicle element has manufactured or tested hardware. An RS-25 liquid propellant engine was hotfire-tested at NASA's Stennis Space Center, Miss. for the first time since 2009 exercising and validating the new engine controller, the renovated A-1 test stand, and the test teams. Four RS-25s will power the SLS core stage. A qualification five-segment solid rocket motor incorporating several design, material, and process changes was scheduled to be test-fired in March at the prime contractor's facility in Utah. The booster also successfully completed its Critical Design Review (CDR) validating the planned design. All six major manufacturing tools for the core stage are in place at the Michoud Assembly Facility in Louisiana, and have been used to build numerous pieces of confidence, qualification, and even flight hardware, including barrel sections, domes and rings used to assemble the world's largest rocket stage. SLS Systems Engineering accomplished several key tasks including vehicle avionics software and hardware build and testing, scale model acoustic and base heating tests. Construction of the Interim Cryogenic Propulsion Stage (ICPS) began. Advanced development provided a look into the future of SLS. Shell buckling knockdown factor testing refined decades-old design margins that added thousands of pounds to rocket payloads. Adaptive manufacturing and structured light scanning development promised to cut the cost and time associated with manufacturing and testing. This paper will provide an overview of the progress made over the past year and provide a glimpse of 2015 milestones and beyond on the way to the first launch in 2018.

May, Todd↗
NASA NTRS2015

NASA's Space Launch System Program Update

Hardware and software for the world's most powerful launch vehicle for exploration is being welded, assembled, and tested today in high bays, clean rooms and test stands across the United States. NASA's Space Launch System (SLS) continued to make significant progress in 2014 with more planned for 2015, including firing tests of both main propulsion elements and the program Critical Design Review (CDR). Developed with the goals of safety, affordability, and sustainability, SLS will still deliver unmatched capability for human and robotic exploration. The initial Block 1 configuration will deliver more than 70 metric tons of payload to low Earth orbit (LEO). The evolved Block 2 design will deliver some 130 metric tons to LEO. Both designs offer enormous opportunity and flexibility for larger payloads, simplifying payload design as well as ground and on-orbit operations, shortening interplanetary transit times, and decreasing overall mission risk. Over the past year, every vehicle element has manufactured or tested hardware. An RS-25 liquid propellant engine was hotfire-tested at NASA's Stennis Space Center, Miss. for the first time since 2009 exercising and validating the new engine controller, the renovated A-1 test stand, and the test teams. Four RS-25s will power the SLS core stage. A qualification five-segment solid rocket motor incorporating several design, material, and process changes was scheduled to be test-fired in March at the prime contractor's facility in Utah. The booster also successfully completed its Critical Design Review (CDR) validating the planned design. All six major manufacturing tools for the core stage are in place at the Michoud Assembly Facility in Louisiana, and have been used to build numerous pieces of confidence, qualification, and even flight hardware, including barrel sections, domes and rings used to assemble the world's largest rocket stage. SLS Systems Engineering accomplished several key tasks including vehicle avionics software and hardware build and testing, scale model acoustic and base heating tests. Construction of the Interim Cryogenic Propulsion Stage (ICPS) began. Advanced development provided a look into the future of SLS. Shell buckling knockdown factor testing refined decades-old design margins that added thousands of pounds to rocket payloads. Adaptive manufacturing and structured light scanning development promised to cut the cost and time associated with manufacturing and testing. This paper will provide an overview of the progress made over the past year and provide a glimpse of 2015 milestones and beyond on the way to the first launch in 2018.

May, Todd↗
NASA NTRS1990

Executing CLIPS expert systems in a distributed environment

This paper describes a framework for running cooperating agents in a distributed environment to support the Intelligent Computer Aided Design System (ICADS), a project in progress at the CAD Research Unit of the Design Institute at the California Polytechnic State University. Currently, the systems aids an architectural designer in creating a floor plan that satisfies some general architectural constraints and project specific requirements. At the core of ICADS is the Blackboard Control System. Connected to the blackboard are any number of domain experts called Intelligent Design Tools (IDT). The Blackboard Control System monitors the evolving design as it is being drawn and helps resolve conflicts from the domain experts. The user serves as a partner in this system by manipulating the floor plan in the CAD system and validating recommendations made by the domain experts. The primary components of the Blackboard Control System are two expert systems executed by a modified CLIPS shell. The first is the Message Handler. The second is the Conflict Resolver. The Conflict Resolver synthesizes the suggestions made by the domain experts, which can be either CLIPS expert systems, or compiled C programs. In DEMO1, the current ICADS prototype, the CLIPS domain expert systems are Acoustics, Lighting, Structural, and Thermal; the compiled C domain experts are the CAD system and the User Interface.

Taylor, James↗
NASA NTRS1986

Ultraviolet and visual variability of Theta CrB during a normal B-phase following a shell phase (1980-1985)

Based on far-UV and visual observations made between 1980 and 1985, the phenomena characterizing the end of a shell phase of Theta-CrB, and the normal B-phase following it, are described as part of a long-term study of Be stars. The strength, shape, and velocity of the C IV, Si IV, and Al III resonance lines, and the Fe III lines of low excitation, show associated variability patterns over the whole range of ionization observable in the IUE and visual spectra. The observed variability pattern consists of a one-year narrow-line stage where the lines show narrow absorption cores close to rest wavelength, a two-year series of abrupt changes between a weak and a strong line, and a damping out of these variations leaving the observed spectrum in a lower ionization state. The existence of a phase-lag between similar phenomena occurring in the superionized and subionized/normally ionized regions, is noted.

Doazan, V.↗
NASA NTRS1975

Angular distributions of electrons of energy E sub e greater than 0.06 MeV in the Jovian magnetosphere

The results of an angular distribution analysis of the electron intensity data recorded near Jupiter for the period from 26 November to 14 December 1973 are presented. The data were from three directional particle detectors with effective integral electron energy thresholds of 0.06, 0.55, and 5.0 Mev, respectively. It was found that the central core of the magnetosphere, within 12 Jupiter radii, is dominated by pitch angle distributions strongly peaked at alpha = 90 deg, while the region from 12 to 25 Jupiter radii shows bidirectional and approximately equal maxima at alpha = 0 and 180 deg. Bidirectional angular distributions in the magnetodisc out to the radius of the magnetopause strongly suggest quasi-trapping on closed field lines as the predominant situation. Substantial field aligned, unidirectional streaming was detected on only two occasions. No distinctive effects on angular distributions were discerned near the L-shells of satellites.

Sentman, D. D.↗
NASA NTRS1984

The remarkable ultraviolet spectrum of the planetary nebula Abell 30

Abell 30 has been identified as a planetary nebula in which the nucleus has experienced a final helium shell flash after ejection of the original, outer envelope. Around the central star of the nebula, four knots of material are observed. In view of the importance of the chemical composition of the ejected material for studies of advanced stages of stellar evolution, clarification of the physical conditions in the knots is vital. Data obtained of Abell 30 with the aid of the International Ultraviolet Explorer (IUE) satellite are discussed along with aspects of extinction, the He II flux, ionic abundances, the C II lambda 4267 line, questions regarding the existence of a carbon-rich core in the knot, the heating of the nebular gas, the central star, and heating by suprathermal particles from the stellar wind. The UV spectrum of the inner nebulosity of Abell 30 indicates that an extraordinary amount of energy is being deposited in the gas.

Harrington, J. P.↗
NASA NTRS1974

Results from the Apollo passive seismic experiment

Recent results from the Apollo seismic network suggest that primitive differentiation occurred in the outer shell of the moon to a depth of approximately 300 km; and the central region of the moon is presently molten to a radius of between 200 and 300 km. If early melting to a depth of 300 to 400 km was a consequence of accretional energy, very short accretion times are required. The best model for the zone of original differentiation appears to be a crust 40 to 80 km thick, ranging in composition from anorthositic gabbro to gabbro; overlying an ultramafic cumulate (olivine-pyroxene) about 250 km thick. The best candidate for the molten core appears to be iron or iron sulphide. A new class of seismic signals has recently been identified that may correspond to shallow moonquakes. These are rare, but much more energetic than the more numerous, deep moonquakes.

Lathum, G.↗
NASA NTRS1977

Results from the Apollo passive seismic experiment

Recent results from the Apollo Seismic Network suggest that primitive differentiation occurred in the outer shell of the moon to a depth of approximately 300 km and the central region of the moon is presently molten to a radius of between 200 and 300 km. If early melting to a depth of 300 to 400 km was a consequence of accretional energy, very short accretion times are required. It was shown that the best model for the zone of original differentiation is a crust 40 to 80 km thick, ranging in composition from anorthositic gabbro to gabbro, and overlying an ultramafic cumulate about 250 km thick. The best candidate for the molten core appears to be iron or iron sulphide. A new class of seismic signals recently were identified that may correspond to shallow moonquakes. These are rare, but much more energetic than the more numerous, deep moonquakes.

Latham, G.↗
NASA NTRS1981

Accreting white dwarf models for type 1 supernovae. 1: Presupernova evolution and triggering mechanisms

As a plausible explosion model for a Type I supernova, the evolution of carbon-oxygen white dwarfs accreting helium in binary systems was investigated from the onset of accretion up to the point at which a thermonuclear explosion occurs. The relationship between the conditions in the binary system and the triggering mechanism for the supernova explosion is discussed, especially for the cases with relatively slow accretion rate. It is found that the growth of a helium zone on the carbon-oxygen core leads to a supernova explosion which is triggered either by the off-center helium detonation for slow and intermediate accretion rates or by the carbon deflagration for slow and rapid accretion rates. Both helium detonation and carbon deflagration are possible for the case of slow accretion, since in this case the initial mass of the white dwarf is an important parameter for determining the mode of ignition. Finally, various modes of building up the helium zone on the white dwarf, namely, direct transfer of helium from the companion star and the various types and strength of the hydrogen shell flashes are discussed in some detail.

Nomoto, K.↗
NASA NTRS1994

The conductive propagation of nuclear flames. 2: Convectively bounded flames in C + O and O + Ne + Mg cores

We determine the speeds, and many other physical properties, of flame fronts that propagate inward into degenerate and semidegenerate cores of carbon and oxygen (CO) and neon and oxygen (NeOMg) white dwarfs when such flames are bounded on their exterior by a convective region. Combustion in such fronts, per se, is incomplete, with only a small part of the initial mass function burned. A condition of balanced power is set up in the star where the rate of energy emitted as neutrinos from the convective region equals the power available from the unburned fuel that crosses the burning front. The propagation of the burning front itself is in turn limited by the temperature at the base of the convective shell, while cannot greatly exceed the adiabatic value. Solving for consistency between these two conditions gives a unique speed for the flame. Typical values for CO white dwarfs are a few hundredths of a centimeter per second. Flames in NeOMg mixtures are slower. Tables are presented in a form that can easily be implemented in stellar evolution codes and yield the rate at which the convective shell advances into the interior. Combining these velocities with the local equations for stellar structure, we find a minimum density for each gravitational potential below with the local equations for stellar structure, we find a minimum density for each gravitational potential below which the flame cannot propagate, and must die. Although detailed stellar models will have to be constructed to reslove some issues conclusively, our results that a CO white dwarf inginted at its edge will not burn carbon all the way to its center unless the mass of the white dwarf exceeds 0.8 solar mass. On the other hand, it is difficult to ignite carbon burning by compression alone anywhere in a white dwarf whose mass does not exceed 1.0 solar mass. Thus, compressionally ignited shell carbon burning in an accerting CO dwarf almost certainly propagates all the way to the center of the star. Implications for neutron star formation, and Type Ia supernova models, are briefly discussed. These are also applicable to massive stars in the about 10-12 solar mass range which ignite neon burning off center.

Timmes, F. X.↗
NASA NTRS2007

The Suzaku Observation of the Nucleus of the Radio Loud Active Galaxy Centaurus A: Constraints on Abundances in the Accreting Material

A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3 to 250 keV. The hard X-rays are fit by two power laws, absorbed by columns of 1.5 and 7 x 10(exp 23) per square centimeter. The dual power-laws are consistent with previous suggestions that the powerlaw components are X-ray emission from the sub-pc VLBI jet and from Bondi accretion at the core, or are consistent with a partial covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature VAPEC model, plus a third power-law component to account for scattered nuclear emission, kpc-scale jet emission, and emission from X-ray Binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca and Ni are detected. The width of the Fe Ka line yields a 200 light-day lower limit on the distance from the black hole to the line-emitting gas. K-shell absorption edges due to Fe, Ca, and S are detected. Elemental abundances are constrained via the fluorescent lines strengths, absorption edge depths and the diffuse plasma emission lines. The high metallicity ([Fe/H]=+0.l) of the circumnuclear material compared to that in the metal-poor outer halo suggests that the accreting material could not have originated in the outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.

Markowitz, A.↗
NASA NTRS2010

Maintaining a Local Data Integration System in Support of Weather Forecast Operations

Since 2000, both the National Weather Service in Melbourne, FL (NWS MLB) and the Spaceflight Meteorology Group (SMG) have used a local data integration system (LDIS) as part of their forecast and warning operations. Each has benefited from 3-dimensional analyses that are delivered to forecasters every 15 minutes across the peninsula of Florida. The intent is to generate products that enhance short-range weather forecasts issued in support of NWS MLB and SMG operational requirements within East Central Florida. The current LDIS uses the Advanced Regional Prediction System (ARPS) Data Analysis System (ADAS) package as its core, which integrates a wide variety of national, regional, and local observational data sets. It assimilates all available real-time data within its domain and is run at a finer spatial and temporal resolution than current national- or regional-scale analysis packages. As such, it provides local forecasters with a more comprehensive and complete understanding of evolving fine-scale weather features. Recent efforts have been undertaken to update the LDIS through the formal tasking process of NASA's Applied Meteorology Unit. The goals include upgrading LDIS with the latest version of ADAS, incorporating new sources of observational data, and making adjustments to shell scripts written to govern the system. A series of scripts run a complete modeling system consisting of the preprocessing step, the main model integration, and the post-processing step. The preprocessing step prepares the terrain, surface characteristics data sets, and the objective analysis for model initialization. Data ingested through ADAS include (but are not limited to) Level II Weather Surveillance Radar- 1988 Doppler (WSR-88D) data from six Florida radars, Geostationary Operational Environmental Satellites (GOES) visible and infrared satellite imagery, surface and upper air observations throughout Florida from NOAA's Earth System Research Laboratory/Global Systems Division/Meteorological Assimilation Data Ingest System (MADIS), as well as the Kennedy Space Center ICape Canaveral Air Force Station wind tower network. The scripts provide NWS MLB and SMG with several options for setting a desirable runtime configuration of the LDIS to account for adjustments in grid spacing, domain location, choice of observational data sources, and selection of background model fields, among others. The utility of an improved LDIS will be demonstrated through postanalysis warm and cool season case studies that compare high-resolution model output with and without the ADAS analyses. Operationally, these upgrades will result in more accurate depictions of the current local environment to help with short-range weather forecasting applications, while also offering an improved initialization for local versions of the Weather Research and Forecasting model.

Watson, Leela R.↗
NASA NTRS1998

Vehicle and Mission Design Options for the Human Exploration of Mars/Phobos Using "Bimodal" NTR and LANTR Propulsion

The nuclear thermal rocket (NTR) is one of the leading propulsion options for future human missions to Mars because of its high specific impulse (Isp-850-1000 s) capability and its attractive engine thrust-to-weight ratio (approximately equal 3-10). To stay within the available mass and payload volume limits of a "Magnum" heavy lift vehicle, a high performance propulsion system is required for trans-Mars injection (TMI). An expendable TMI stage, powered by three 15 thousand pounds force (klbf) NTR engines is currently under consideration by NASA for its Design Reference Mission (DRM). However, because of the miniscule burnup of enriched uranium-235 during the Earth departure phase (approximately 10 grams out of 33 kilograms in each NTR core), disposal of the TMI stage and its engines after a single use is a costly and inefficient use of this high performance stage. By reconfiguring the engines for both propulsive thrust and modest power generation (referred to as "bimodal" operation), a robust, multiple burn, "power-rich" stage with propulsive Mars capture and reuse capability is possible, A family of modular "bimodal" NTR (BNTR) vehicles are described which utilize a common "core" stage powered by three 15 klbf BNTRs that produce 50 kWe of total electrical power for crew life support, an active refrigeration / reliquification system for long term, "zero-boiloff" liquid hydrogen (LH 2 ) storage, and high data rate communications. An innovative, spine-like "saddle truss" design connects the core stage and payload element and is open underneath to allow supplemental "in-line" propellant tanks and contingency crew consumables to be easily jettisoned to improve vehicle performance. A "modified" DRM using BNTR transfer vehicles requires fewer transportation system elements, reduces IMLEO and mission risk, and simplifies space operations. By taking the next logical step--use of the BNTR for propulsive capture of all payload elements into Mars orbit--the power available in Mars orbit grows to 150 kWe compared to 30 kWe for the DRM. Propulsive capture also eliminates the complex, higher risk aerobraking and capture maneuver which is replaced by a simpler reentry using a standardized, lower mass "aerodescent" shell. The attractiveness of the "all BNTR" option is further increased by the substitution of the lightweight, inflatable "TransHab" module in place of the heavier, hard-shell hab module. Use of TransHab introduces the potential for propulsive recovery and reuse of the BNTR/ERV. It also allows the crew to travel to and from Mar on the same BNTR transfer vehicle thereby cutting the duration of the ERV mission in half--from approximately 4.7 to 2.5 years. Finally, for difficult Mars options, such as Phobos rendezvous and sample return missions, volume (not mass) constraints limit the performance of the "all LH 2 " BNTR stage. The use of "LOX-augmented" NTR (LANTR) engines, operating at a modest oxygen-to-hydrogen mixutre ratio (MR) of 0.5, helps to increase "bulk" propellant density and total thrust during the TMI burn. On all subsequent burns, the bimodal LANTR engines operate on LH 2 only (MR=0) to maximize vehicle performance while staying within the lift capability of two Magnum launches.

Nuclear thermal rocket↗
NASA NTRS2002

Vehicle and Mission Design Options for the Human Exploration of Mars/Phobos Using "Bimodal" NTR and LANTR Propulsion

The nuclear thermal rocket (NTR) is one of the leading propulsion options for future human missions to Mars because of its high specific impulse (lsp~850-1000 s) capability and its attractive engine thrust-to-weight ratio (~3-10). To stay within the available mass and payload volume limits of a “Magnum” heavy lift vehicle, a high performance propulsion system is required for trans-Mars injection (TMI). An expendable TMI stage, powered by three 15 thousand pounds force (klbf) NTR engines is currently under consideration by NASA for its Design Reference Mission (DRM). However, because of the miniscule burnup of enriched uranium-235 during the Earth departure phase (~10 grams out of 33 kilograms in each NTR core), disposal of the TMI stage and its engines after a single use is a costly and inefficient use of this high performance stage. By reconfiguring the engines for both propulsive thrust and modest power generation (referred to as “bimodal” operation), a robust, multiple burn, “power-rich” stage with propulsive Mars capture and reuse capability is possible. A family of modular “bimodal” NTR (BNTR) vehicles are described which utilize a common “core” stage powered by three 15 klbf BNTRs that produce 50 kWe of total electrical power for crew life support, an active refrigeration / reliquification system for long term, zero-boiloff liquid hydrogen (LH 2 ) storage, and high data rate communications. An innovative, spine-like “saddle truss” design connects the core stage and payload element and is open underneath to allow supplemental “in-line” propellant tanks and contingency crew consumables to be easily jettisoned to improve vehicle performance. A “modified” DRM using BNTR transfer vehicles requires fewer transportation system elements, reduces IMLEO and mission risk, and simplifies space operations. By taking the next logical step—use of the BNTR for propulsive capture of all payload elements into Mars orbit—the power available in Mars orbit grows to 150 kWe compared to 30 kWe for the DRM. Propulsive capture also eliminates the complex, higher risk aerobraking and capture maneuver which is replaced by a simpler reentry using a standardized, lower mass “aerodescent” shell. The attractiveness of the “all BNTR” option is further increased by the substitution of the lightweight, inflatable “TransHab” module in place of the heavier, hard-shell hab module. Use of TransHab introduces the potential for propulsive recovery and reuse of the BNTR / Earth return vehicle (ERV). It also allows the crew to travel to and from Mars on the same BNTR transfer vehicle thereby cutting the duration of the ERV mission in half—from ~4.7 to 2.5 years. Finally, for difficult Mars options, such as Phobos rendezvous and sample return missions, volume (not mass) constraints limit the performance of the “all LH 2 ” BNTR stage. The use of “LOX-augmented” NTR (LANTR) engines, operating at a modest oxygen-to-hydrogen mixture ratio (MR) of 0.5, helps to increase “bulk” propellant density and total thrust during the TMI burn. On all subsequent burns, the bimodal LANTR engines operate on LH 2 only (MR=0) to maximize vehicle performance while staying within the mass limits of two Magnum launches.

Nuclear thermal rocket↗
NASA NTRS1974

Stress, stability and vibration of complex, branched shells of revolution

A comprehensive computer program, designated BOSOR4, for analysis of the stress, stability, and vibration of segmented, ring-stiffened, branched shells of revolution and prismatic shells and panels is described. The program performs large-deflection axisymmetric stress analysis, small-deflection nonsymmetric stress analysis, modal vibration analysis with axisymmetric nonlinear prestress included, and buckling analysis with axisymmetric or nonsymmetric prestress. One of the main advantages of the code is the provision for realistic engineering details such as eccentric load paths, internal supports, arbitrary branching conditions, and a 'library' of wall constructions. The program is based on the finite-difference energy method, which is very rapidly convergent with increasing numbers of mesh points. The organization of the program is briefly described with the flow of calculations charted for each of the types of analysis. Overlay charts and core storage requirements are given for the CDC 6600, IBM 370/165, and UNIVAC 1108 versions of BOSOR4.

Bushnell, D.↗
NASA NTRS1994

A study of a high resolution IUE spectrum of AM Canum Venaticorum

We have obtained the first high resolution IUE spectrum of the helium-rich, cataclysmic variable star AM CVn. The spectrum is greatly underexposed, but we can still detect both wide and narrow line profiles. We report broad, shortward-shifted, P-Cygni-like absorption and in some cases emission lines in the far UV high ionization resonance lines of C, N, O, and Si, but the profiles are considerably disk/boundary layer outflows, absorption disk continuum light in H-rich CVs. The highest ionizations show evidence of a narrow jet or conical flow. For other, lower ionized lines, we find some evidence of a stellar origin. The broad He II (lambda 1640 A) absorption profile with blue shifted emission core has a remarkably similar overall structure to the He II (lambda 1640 A) broad absorption trough in the IUE spectrum of the prototypical cool DO white dwarf HZ 21. The sharp absorption lines seem most convincingly in the resonance doublets of N V (lambda 1238 A, lambda 1242 A) and C IV (lambda 1548 A, lambda 1550 A) and in He II (lambda 1640 A) exhibit a precise velocity coincidence. These sharp features are almost certainly due to circumbinary matter because they are obviously unaffected by the rapid orbital motion (or rapid stellar rotation) in this short period system during the long (9.3 hour) IUE echelle exposure. Our observations support an evolution through shell episodes of a close binary system which ends up with an expanding envelope as seen for HZ 21, and suggests one possible evolutionary channel for production of DOs (DBs).

Solheim, J.-E.↗